During seed germination, iron (Fe) stored in vacuoles is exported by the redundant NRAMP3 and NRAMP4 transporter proteins. A double nramp3 nramp4 mutant is unable to mobilize Fe stores and does not develop in the absence of external Fe. We used RNA sequencing to compare gene expression in nramp3 nramp4 and wild type during germination and early seedling development. Even though sufficient Fe was supplied, the Fe-responsive transcription factors bHLH38, 39, 100 and 101 and their downstream targets FRO2 and IRT1 mediating Fe uptake were strongly upregulated in the nramp3 nramp4 mutant...

Photoproduction of hydrogen by green algae is considered a transitory release valve of excess reducing power and a potential carbon-free source of sustainable energy. It is generally accepted that the transitory production of hydrogen is governed by fast inactivation of hydrogenase by oxygen. However, our data suggest that photosynthetic electron loss to competing processes, mainly carbon fixation, stops hydrogen production, supports hydrogen uptake and precedes the inevitable inactivation by oxygen. Here we show that when transitioning from dark anaerobiosis to light, hydrogen production ceases within 2 minutes, regardless of the presence of oxygen...

DAWDLE (DDL) is a conserved forkhead-associated (FHA) domain-containing protein with essential roles in plant development and immunity. It acts in the biogenesis of microRNAs (miRNAs) and endogenous small interfering RNAs (siRNAs), which regulate gene expression at the transcriptional and/or post-transcriptional levels. However, the functional mechanism of DDL and its impact on exogenous siRNAs remain elusive. Here we report that DDL is required for the biogenesis of siRNAs derived from sense transgenes and inverted-repeat transgenes...

Cell walls are crucial for the integrity and function of all land plants, and are of central importance in human health, livestock production, and as a source of renewable bioenergy. Many enzymes that mediate the biosynthesis of cell wall polysaccharides are encoded by members of the large cellulose synthase (CesA) gene superfamily. Here, we analyzed 29 sequenced genomes and 17 transcriptomes to revise the phylogeny of the CesA gene superfamily in angiosperms. Our results identify ancestral gene clusters that predate the monocot-eudicot divergence and reveal several novel evolutionary observations, including the expansion of the Poaceae-specific cellulose synthase-like CslF family to the graminids and restiids and the characterisation of a previously unreported eudicot lineage, CslM, that forms a reciprocally monophyletic eudicot-monocot grouping with the CslJ clade...

Phosphatidylcholine (PC) is a major membrane phospholipid and a precursor for most signalling molecules. Understanding its synthesis is important for improving plant growth, nutritional value and resistance to stress. PC synthesis is complex, involving several interconnected pathways, one of which proceeds from serine-derived phosphoethanolamine (PEA) to form phosphocholine (PCho) through three sequential phospho-base methylations catalysed by phosphoethanolamine N-methyltransferases (PEAMTs). The contribution of this pathway to the production of PC and plant growth has been a matter of some debate...

Marine diatoms are prominent phytoplankton organisms, optimally performing photosynthesis in extremely variable environments. Diatoms possess a strong ability to dissipate excess absorbed energy as heat via non-photochemical quenching (NPQ). This process relies on changes in carotenoid pigment composition (xanthophyll cycle) and on specific members of the light-harvesting complex (LHC) family specialized in photoprotection (LHCX), which potentially act as NPQ effectors. However, the link between light stress, NPQ, and the existence of different LHCX isoforms is not understood in these organisms...

Algae undergo a complete metabolic transformation under stress by arresting cell growth, inducing autophagy, and hyper-accumulating biofuel precursors such as triacylglycerols and starch. However, the regulatory mechanisms behind this stress-induced transformation are still unclear. Here, we use biochemical, mutational, and 'omics' approaches to demonstrate that phosphatidylinositol 3-kinase (PI3K) signaling mediates the homeostasis of energy molecules and influences carbon metabolism in algae. In Chlamydomonas reinhardtii, the inhibition and knockdown (KD) of algal class III PI3K led to significantly decreased cell growth, altered cell morphology, and higher lipid and starch contents...

Cold stress is a major factor limiting rice (Oryza sativa L.) production worldwide, especially at the seedling and booting stages. Identification of genes associated with cold tolerance (CT) in rice is important for sustainable food production. Here, we report the results of a genome-wide association study (GWAS) to identify the genetic loci associated with CT by using a 1,033-accession diversity panel. We identified five CT-related genetic loci at the booting stage. Accessions carrying multiple cold-tolerant alleles displayed a higher seed setting rate than did accessions that had no cold-tolerant alleles or carried a single allele...

Leaf senescence is an essential physiological process in plants that supports the recycling of nitrogen and other nutrients to support the growth of developing organs, including young leaves, seeds and fruits. Thus, the regulation of senescence is crucial for evolutionary success in wild populations and for increasing yield in crops. Here we describe the influence of a NAC transcription factor, SlNAP2 (Solanum lycopersicum NAC-like, activated by apetala3/pistillata), that controls both leaf senescence and fruit yield in tomato (Solanum lycopersicum)...

Glycosylinositol phosphorylceramides (GIPCs), which have a ceramide core linked to a glycan headgroup of varying structure, are the major sphingolipids in the plant plasma membrane. Recently, we identified the major biosynthetic genes for GIPC glycosylation in Arabidopsis thaliana, and demonstrated that the glycan headgroup is essential for plant viability. However, the function of GIPCs and the significance of their structural variation are poorly understood. Here, we characterized the Arabidopsis glycosyltransferase GLUCOSAMINE INOSITOLPHOSPHORYLCERAMIDE TRANSFERASE1 (GINT1) and showed that it is responsible for the glycosylation of a subgroup of GIPCs found in seeds and pollen that contain N-acetylglucosamine (GlcNAc) and glucosamine (GlcN; collectively GlcN(Ac))...

Photoautotrophic organisms must efficiently allocate their resources between stress-response pathways and growth-promoting pathways to be successful in a constantly changing environment. In this study, we addressed the coordination of sulfur flux between biosynthesis of the reactive oxygen species scavenger glutathione (GSH) and protein translation as one example of a central resource allocation switch. We crossed the Arabidopsis (Arabidopsis thaliana) GSH synthesis depleted cadmium-sensitive cad2-1 mutant, which lacks glutamate Cys ligase, into the sulfite reductase (SiR) sir1-1 mutant, which suffers from a significantly decreased flux of sulfur into cysteine and is consequently retarded in growth...

Recent progress in root phenotyping has focused mainly on increasing throughput for genetic studies while identifying root developmental patterns has been comparatively underexplored. We introduce a new phenotyping pipeline for producing high-quality spatio-temporal root system development data and identifying developmental patterns within these data. The SmartRoot image analysis system and temporal and spatial statistical models were applied to two cereals, pearl millet (Pennisetum glaucum) and maize (Zea mays)...

Plant chloroplasts constantly accumulate damage caused by visible light during photosynthesis. Our previous study revealed that entire photodamaged chloroplasts are subjected to vacuolar digestion through an autophagy process termed chlorophagy; however, how this process is induced and executed remained poorly understood. In the current study, we monitored intracellular induction of chlorophagy in Arabidopsis leaves, and found that mesophyll cells damaged by high visible light (HL) displayed abnormal chloroplasts with a swollen shape and 2...

The hormone abscisic acid (ABA) plays a critical role in enhancing plant survival during water deficit. Recent molecular evidence suggests that ABA is synthesized in the phloem companion cells and guard cells. However, the nature of cell turgor and water status in these two cell types cannot easily account for the rapid, water status-triggered ABA biosynthesis observed in leaves. Here we utilize the unique foliar anatomies of an angiosperm (Hakea lissosperma) and of four conifer species (Saxegothaea conspicua, Podocarpus latifolius, Cephalotaxus harringtonii, and Amentotaxus formosana) in which the mesophyll can be isolated from the vascular tissue to identify the main site of ABA biosynthesis in water-stressed leaves...

Plants sense and respond to light via multiple photoreceptors including phytochrome. The decreased ratio of red to far-red light that occurs under a canopy triggers shade avoidance responses, which allow plants to compete with neighbouring plants. The leaf acts as a photoperceptive organ in this response. In the present study, we investigated how the shade stimulus is spatially processed within the cotyledon. We performed transcriptome analysis on micro-tissue samples collected from vascular and non-vascular regions of Arabidopsis thaliana cotyledons...

Boron (B) is an essential element for plants; however, as high B concentrations are toxic, B transport must be tightly regulated. BOR1 is a borate exporter in Arabidopsis thaliana that facilitates B translocation into shoots under B deficiency conditions. When the B supply is sufficient, BOR1 expression is downregulated by selective degradation of BOR1 protein, while additional BOR1 regulatory mechanisms are proposed to exist. In this study, we identified a novel B-dependent BOR1 translational suppression mechanism...

The commelinid monocotyledons make up a monophyletic clade differentiated from other monocotyledons by the presence of cell-wall-bound ferulate and p-coumarate. The Poaceae or grass family is a member of this group and it is known that most of the p-coumarate in the cell walls of this family acylates lignin. Here, we isolated and examined lignified cell-wall preparations from 10 species of commelinid monocotyledons from nine families, outside the Poaceae, including species from all four commelinid monocotyledon orders Poales, Zingiberales, Commelinales, and Arecales...

Endopolyploidy occurs when DNA replication takes place without subsequent mitotic nuclear division, resulting in cell-specific ploidy levels within tissues. In plants, endopolyploidy plays an important role in sustaining growth and development, but only a few studies have demonstrated a role in abiotic stress response. In this study, we investigated the function of ploidy level and nuclear and cell size in leaf expansion throughout development and tracked cell-type specific ploidy in the halophyte Mesembryanthemum crystallinum...